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Thread: new ball valve leaks at stem

  1. #1

    Default new ball valve leaks at stem

    I am an amateur plumber and have done many non-solder plumbing over the years. Now I am re-modelling a bathroom shower. I installed shut-off valves for hot & cold lines, so that I can work in the shower without getting soaked. The 1/2 inch supply lines in the wall are vertical. I cut open an access hole in the back side of the shower wall. I bought ball-type valves. I kept the valves in the open position while soldering.

    QUESTION: How do I keep the valve from leaking at the stem? I have tightened the nut on the valve stem 5 or 6 times over the last 2 days, but there is still a slow drip, every few seconds. Is it possible the valve was damaged due to heat from soldering? I sweated the top side of the valve first, then the bottom. It took several minutes to get the joint hot enough to melt the solder, and I had to do this twice, for top and bottom. Also one joint had a slow leak so I had to re-heat it again and add more solder.

    I do not mind cutting out the valve and starting over, but I am not sure what I would do different. If I do start over, I suppose I could sweat the valve joints before installing them, and then solder a mating coupler at the top and bottom which takes less heat to solder than the cast alloy body of the shut-off ball valves.

  2. #2
    Plumber Cass's Avatar
    Join Date
    Nov 2005


    It sounds lke you may have over heated them...I would bring them back to the big box store if that s where you bought them... their policy is you can return them for any reason at all. The next time you do it you need to heat the fitting qiuckly, apply the solder, then try cooling it quickly with a wet cloth. This will help protect the inside of the valve...

    Better still just do your work with the water off then turn it on when you are finished.

    Don't even mess with the valve.

  3. #3
    Plumber gear junkie's Avatar
    Join Date
    Feb 2008
    Virginia Beach, IPC country


    Can you post a pic of your ball valve? Want to make sure we're talking about the same thing. Solder with mapp gas, works better.

  4. #4
    One who lurks Basement_Lurker's Avatar
    Join Date
    Jun 2007
    Victoria, BC


    No offense to gear junkie, but my advice would be for you to stay away from MAPP gas for now. It burns hotter than propane, and since you are admittedly amateurish at soldering and because you warped these valves due to overheating the joint/fitting, you need to learn how to heat up a joint properly without overheating it so that you don't burn away the flux or melt valves

    My suggestion to you is to not heat the fitting directly as it sounds like you did...heating a ball valve unit like that will surely warp it even in the open position! Heat the section of copper about a 1/2" below the valve joint until you see the flux start to begin to bubble, then quickly move your flame to the valve for a few seconds, and then back down below the joint and apply the solder to the joint. If the solder gets sucked up into the joint nicely, you can move the flame a 1/2" above the valve now and probably immediately add solder to the other valve joint.

    Oh, and whatever you do, don't let the flame heat the handle side of the ball valve, even if it's a mini ball valve with an all metal handle!
    Broken promises don't upset me. I just think, why did they believe me? -Jack Handy


  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    If water gets into a leaky connection, the only reliable way to fix it is to remove it, clean it, flux it and try again. Adding solder after it got wet is not reliable.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    Senior Robin Hood Guy Ian Gills's Avatar
    Join Date
    Jul 2007


    I will be doing this same job at the weekend. So thanks for the tips.


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